The present invention relates to chemical treatments for oil and gas wells. More particularly, the present invention relates to methods and compositions for enhancing the coverage and displacement of treatment fluids into subterranean formations.
Chemical treatments for oil and gas wells often involve sequential injections of one or more fluids, such as a preflush, chemical agent, spacer, and/or afterflush. Typically treatment fluids are injected into a subterranean formation at the matrix flow rate, i.e., the rate at which the treatment fluid enters laminar flow inside the formation. At this rate the treatment fluid enters the interstitial spaces of the formation at a flow rate low enough to avoid generating areas of high pressure within the formation that could cause the formation to fracture inadvertently. The success of these treatments often relies on the effective coverage and displacement of one fluid by another. Unfortunately, problems of uneven distribution or placement of treatment fluids are often encountered in well bores containing multiple layers with highly variable permeabilities.
Previously, acid stimulation treatments have applied Paccaloni's maximum pressure differential and injection rate (“MAPDIR”) method, which uses the injection rate as the key parameter to obtain a desired bottomhole pressure differential. However, Paccaloni's MAPDIR method and other methods involving high injection rates have not been widely adopted outside of acid stimulation treatments. This is due to the fact that many other treatment fluids, such as curable resins, are too viscous to be pumped into a formation at a flow rate sufficiently high enough to maximize the pressure differential without fear of inadvertently fracturing the formation. Furthermore, traditional solvents that could be used to lower the viscosity of the treatment fluids also tend to render the fluids less capable of adequately coating the formation, sometimes defeating the purpose of injecting the fluids into the formation.